Dear Mr. Dad: My wife is breastfeeding our three-month-old baby, but wants to wean the baby and go back to work. I heard somewhere that it’s better for babies to nurse for longer. But does it really matter when she stops? Is there some actual “right” time to introduce solid foods?

A: I teach a class for expectant dads in San Francisco, and that question comes up a lot. The short answer to both of your questions is, ”Yes.” It does matter when your wife weans your baby, and there is a “right time.” The American Academy of Pediatrics (AAP) recommends that, barring any medical reasons to the contrary, babies should have nothing but breast milk for the first six months. Then, gradually introduce solids and phase out the breast milk over the next six months.

However, if you or your wife has—or is at risk of developing—diabetes, that “right time” is more of a window than a hard line: Somewhere between four and five months. Introducing solids too early or too late may cause real problems.

On the too-early end, researchers at the Colorado School of Public Health at the University of Colorado just found that weaning a child before four months doubles the child’s chances of developing type 1 diabetes (which used to be called “juvenile onset” diabetes). So at the very least, you’ll want to encourage your wife to hold off on weaning and keep breastfeeding until four months old.

By the way, extending breastfeeding doesn’t have to interfere with your wife’s return to work. She can pump several bottles of milk at night or in the morning before she goes to work. You or another caregiver can give that milk—and the benefits of breastfeeding—to the baby during the day. Most employers are legally required to provide a place for nursing women to pump (however, that “place” could be a nice lounge or it could just as easily be a stall in the women’s bathroom).

Unfortunately, not enough people follow these guidelines. The Centers for Disease Control and Prevention (CDC) estimates that 40 percent of moms introduce solid food before their baby hits four months. Worse yet, nine percent of moms have given their baby solid food before four weeks.

Okay, let’s talk about the other end of the window. If you’re able to get your wife to breastfeed for four months, see if you can convince her to go all the way to six. Several studies have shown that those two extra months make a huge difference, cutting in half the risk of coming down with an ear infection and/or pneumonia. In addition, for babies with a genetic diabetes risk, the same Colorado study that found that introducing solid foods too soon increases diabetes risk, also found that babies who didn’t get solid foods until after six months had triple the type-1-diabetes risk of those weaned before six months.

“In summary, there appears to be a safe window in which to introduce solid foods between four and five months of age,” wrote Brittni Frederiksen, the study’s lead author. “Solid foods should be introduced while continuing to breastfeed to minimize [type 1 diabetes] risk in genetically susceptible children.”

Remember, introducing solid foods and weaning aren’t always the same thing. In other words, it’s fine to do both at the same time. In fact, the Colorado study found that introducing wheat or barley while continuing to breastfeed actually reduced diabetes risk.

Hopefully, I’ve given you and your wife something to think about. But before you make a final decision about when to wean your baby, make sure to talk with your pediatrician.
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